The present invention relates to latches and latching methods, and more particularly to devices and methods for controlling a latch in its locked and unlocked states and for switching a latch between such states.
Conventional latches are used to restrain the movement of one member or element with respect to another. For example, conventional door latches restrain the movement of a door with respect to a surrounding door frame. The function of such latches is to hold the door secure within the door frame until the latch is released and the door is free to open. Existing latches typically have mechanical connections linking the latch to actuation elements such as handles which can be actuated by a user to release the latch. Movement of the actuation elements is transferred through the mechanical connections and (if not locked) can cause the latch to release. The mechanical connections can be one or more rods, cables, or other suitable elements or devices. Although the following discussion is with reference to door latches (e.g., especially for vehicle doors) for purposes of example and discussion only, the background information and the disclosure of the present invention provided applies equally to a wide variety of latches used in other applications.
Most current vehicle door latches contain a restraint mechanism for preventing the release of the latch without proper authorization. When in a locked state, the restraint mechanism blocks or impedes the mechanical connection between a user-operable handle (or other door opening device) and a latch release mechanism, thereby locking the door. Many conventional door latches also have two or more lock states, such as unlocked, locked, child locked, and dead locked states. Inputs to the latch for controlling the lock states of the latch can be mechanical, electrical, or parallel mechanical and electrical inputs. For example, by the turn of a user""s key, a cylinder lock can mechanically move the restraint mechanism, thereby unlocking the latch. As another example, cable or rod elements connecting a door lock to the restraint mechanism can be controlled by one or more electrical power actuators. These actuators, sometimes called xe2x80x9cpower locksxe2x80x9d can use electrical motors or solenoids as the force generator to change between locked and unlocked states.
An important issue with regard to the design of latch assemblies is the desirability of a latch assembly to operate smoothly. Unless friction is employed to retain one or more elements in desired positions in the latch assembly, low-friction contact (such as contact between rotatably-connected elements) is preferred. In addition, latch assembly designs in which part wear is reduced or eliminated is highly desirable. These latch assembly design considerations significantly limit the number of viable solutions for a number of latch assembly design problems described below.
In most conventional latch designs, one or more elements are moved to release a retaining element holding the latch in a latched position. For example, a pawl can be movable to release a ratchet holding the striker of the latch. The pawl (or other movable element used to hold the ratchet in a latched position) can be moved in many different manners, such as by being rotated, pushed, pulled, shifted, and the like. Typically, one or more elements such as levers are movable by actuation of a handle or other latch assembly input to move the pawl. These pawl-moving elements can be connected directly to the pawl or can otherwise be moved to exert motive force upon the pawl. In either case, preventing inadvertent movement of the pawl by these pawl-moving elements is another important design consideration, and can be accomplished by controlling the position and mobility of the pawl-moving elements in the latch assembly. Such inadvertent movement can be caused in some conventional latch assemblies by employing pawl-moving elements that have a mass close to the pawl and that can react to shock or severe vibration to impart force upon the pawl, by severe impact upon the latch (such as experienced in a vehicle collision or rollover), and by other manners.
Because many pawl-moving elements have locked and unlocked states as described above, such elements must often be moved or movable in different manners corresponding to the locked and unlocked states. Such movement can limit the ability to fully secure and control the pawl-moving element within the latch assembly (both highly desirable features of pawl-moving elements). Therefore, the possible manners in which pawl-moving elements can be connected and move within latch assemblies is often significantly limited.
It is possible to add structure and elements to conventional door latch designs in order to address the above-noted problems and to take into account the latch assembly design considerations described above. However, such additional structure and elements are likely to increase latch complexity. Increased latch complexity also increases assembly and repair cost. Accordingly, the reasonable door latch design alternatives available to address the above-noted problems and design considerations of conventional door latches are significantly limited.
Problems of latch weight and size are related to the problem of latch complexity. The inclusion of more elements and more complex mechanisms within the latch generally undesirably increases the size and weight of the latch. In virtually all vehicle applications, weight and size of any component is a concern. Therefore, many latch designs employing additional structure and elements to address the above-noted problems and to take into account the design considerations described above do so at an unacceptable cost of increased latch weight and size.
Regardless of the mechanism employed to change the locked state of a latch assembly (to disable or enable a mechanical or electrical input to the latch assembly), another problem common to the vast majority of conventional door latches relates to the inability of such door latches to properly respond to multiple inputs at a given time. A well-recognized example of this problem is the inability of most conventional door latches to properly respond to a user unlocking the door latch while the door handle is partially or fully actuated. While this problem can exist for door latches that are not powered, it is particularly problematic in powered latches. For example, a user of a keyless entry system can push a button on a key fob, enter an access code on a door keypad, or otherwise transmit a signal (by wire or wirelessly) to a controller in the vehicle that in turn sends a signal to power unlock a handle input to the latch. In conventional power latches, an amount of time is required for this process to take place. During this time, a user may attempt to unlatch the latch by actuating the handle input. Because the latch has not yet been unlocked, such actuation does nothingxe2x80x94even after the latch has been powered to its unlocked state while the handle input is in a partially or fully actuated position. The user must release the handle, transmit another unlocking signal to power unlock the handle, and then re-actuate the handle to unlatch the latch. In other words, to unlatch a conventional latch, actuation of the handle input must occur after the handle input has been placed in its unlocked state. Partial or full actuation of the handle input before this time will not unlatch the latch and will require the user to release and re-actuate the handle input.
This shortcoming of conventional door latches exists for powered and fully manual door latches alike. In addition to requiring the user to re-actuate an input to unlatch the unlocked latch, this problem can even prevent the latch from changing between its locked and unlocked states. In such a case, the user is required to unlock the latch assembly again (re-transmit a signal to the latch assembly or manually unlock the latch assembly again as described above) after the handle input has been released. Any of the results just described represent an annoying attribute of conventional latch assembly designs. In this and other examples, a conventional latch assembly is unable to respond to actuation of more than one input at a time, or is only responsive to one of two inputs actuated simultaneously or closely in time.
In light of the problems and limitations of the prior art described above, a need exists for a latch assembly that is relatively simple in construction, lightweight, reliable, and easy to assemble and maintain, operates smoothly and efficiently with minimal friction and wear, has pawl-moving elements having improved control and stability, is preferably able to properly respond to an unlocking/locking input and to an latching/unlatching input received simultaneously or closely in time, and does so with minimal to no additional latch assembly elements and structure. Each preferred embodiment of the present invention achieves one or more of these results.
Some preferred embodiments of the present invention employ a pawl releasably engagable with a ratchet latching the door in place, a user-manipulatable handle, a lever movable between an unlocked position in which actuation of the lever by the handle generates sufficient pawl movement to release the ratchet and a locked position in which actuation of the lever by the handle does not generate sufficient pawl movement to release the ratchet, and a locking and unlocking mechanism coupled to the lever for moving the lever between its unlocked and locked positions. In some highly preferred embodiments, the locking and unlocking mechanism is an over-center device capable of moving the lever between its unlocked and locked positions. Also, the lever in some highly preferred embodiments is pivotable about the same or substantially the same location with respect to the lever in the locked and unlocked positions of the lever. In either case and in still other embodiments, the lever can be moved (e.g., by the locking and unlocking mechanism) between a locked position in which the mass of the lever or portion thereof is removed a distance from the pawl and an unlocked position in which the mass of the lever or portion thereof is moved closer to the pawl.
A significant amount of control over the lever is possible when the lever is pivotable in the locked and unlocked positions about the same or substantially the same location with respect to the lever. This location can be (and in some embodiments is) a location where the locking and unlocking mechanism is attached to the lever. By moving this point about which the lever pivots in its various states, the lever can be reliably moved to different locations with respect to the pawl while maintaining a degree of control over lever orientation and action. The pivot point of the lever can be in the same place or substantially the same place with respect to the lever in all positions of the lever in the latch assembly or in only a locked position and an unlocked position of the lever in the latch assembly. Also, the lever can be moved between its locked and unlocked positions by translating and/or rotating the lever or by moving the lever in any other manner desired.
In some embodiments of the present invention, additional control over the lever used to move the pawl is achieved by use of an over-center locking and unlocking mechanism. Specifically, an over-center device can be used to move the lever between its locked and unlocked positions. The over-center device has at least two stable positions separated by an unstable xe2x80x9ccenterxe2x80x9d position. Therefore, when the over-center device is actuated to one side of the center position, the lever connected thereto remains on that side until the over-center device is actuated to the opposite side of the center position. In this manner, the lever can be placed by the over-center device in a locked state in which the lever is in one position with respect to the pawl and in an unlocked state in which the lever is in another position with respect to the pawl. In some embodiments, the over-center device is biased away from the center position in either or both directions, thereby further retaining the lever in its locked or unlocked state until the over-center device is actuated again. In other embodiments, the over-center device is not biased away from the center position in one or both directions. In such embodiments, actuation of the lever can draw the over-center device further away from the center position, thereby ensuring that the lever stays in the locked or unlocked state to which it has already been moved.
The over-center device can take a number of different forms. For example, the over-center device can be or include two elements that are rotatably coupled together at a first pivot point. One of the two elements can be mounted for pivotal movement about a second pivot point and the other element can be pivotably connected at a third pivot point to the lever used to move the pawl. By rotating either element of the over-center device, the other element also rotates and causes the lever to move with respect to the pawl. In some embodiments, the center position of such an over-center device is defined by a line passing through the second and third pivot points, whereby the position of the first pivot with respect to either side of the line determines whether the lever is in a locked or unlocked state.
The two elements in the over-center device just described can take a number of different forms, such as an elongated bar pivotably coupled at one end to the lever and at another end to an edge of a disc that is rotatable about its axis, two links connected in a similar manner, and the like. Other types of over-center devices can be employed, such as an over-center device having a first element connected to or capable of moving the pawl and biased against an inclined surface of a second element. The two stable positions of the over-center device are defined by the first element located at the xe2x80x9ctopxe2x80x9d and xe2x80x9cbottomxe2x80x9d of the inclined surfaces of the second element, respectively (whereby the first element can be retained in a recess, at plateau, on a step, or by another feature located at the top of the inclined surface of the second element). In yet another type of over-center device, a first element is connected to or is otherwise capable of moving the pawl and is biased against the surface of a rotatable second element. The surface is preferably eccentric with respect to the rotational axis of the second element. Therefore, the two stable positions of the over-center device are defined by the first element located at two different rotational positions of the second element (e.g., rotated toward the first element and rotated away from the first element). Still other types of over-center devices can be used as desired.
Although some embodiments of the present invention employ an over-center device with a lever that is pivotable about substantially the same position with respect to the lever in the locked and unlocked states thereof, it should be noted that any other locking and unlocking mechanism can be employed to move the lever as described above. For example, the locking and unlocking mechanism can be a solenoid, hydraulic or pneumatic cylinder, or any other type of actuator. Also, the over-center device can be employed to position a lever that is pivotable about different points with respect to the lever in the locked and unlocked states thereof.
It is desirable in some applications to remove the lever (used to move the pawl) a distance away from the pawl when the lever is in a locked state. More specifically, the mass of the lever that is located nearest to the pawl when the lever is in its unlocked state is preferably removed a distance from the pawl when the lever is in its locked state. In this manner, the opportunity for the lever to be forced toward and against the pawl when the lever is in its locked state is further reduced. For example, protection is increased against lever movement against the pawl causing pawl release as a result of shock, impact, or severe vibration of the latch assembly, such as from a vehicle collision or rollover. Preferably, an over-center device coupled to the lever can be used to move the mass of the lever toward and away from the pawl in the unlocked and locked states of the lever, respectively. However, any locking and unlocking mechanism can be employed to move the lever for this purpose.
In some preferred embodiments of the present invention, the latch assembly is capable of properly responding to unlatching and unlocking inputs received at the same time or closely in time. In other words, when the lever used to move the pawl is actuated before or while a locking and unlocking mechanism is placed in its unlocked state, the latch assembly properly responds by unlatching the latch upon movement of the locking and unlocking mechanism to the unlocked state. In one preferred application involving a car door latch capable of being unlocked via a remote keyless entry system, the user can partially or fully actuate the door handle prior to unlocking the door or while the door is being unlocked (e.g., while the keyless entry system is still processing the request to unlock the latch assembly, during movement of the locking and unlocking mechanism to its unlocked state, and the like). The latch assembly responds by unlatching the latch when the latch assembly is finally unlocked, and does so without requiring the user to release and re-actuate the door handle. Although the other embodiments of the present invention described above can operate without this feature, such latch assembly embodiments preferably have this capability.
More information and a better understanding of the present invention can be achieved by reference to the following drawings and detailed description.